With the development of industry, there has been a rapid growth of interest in a liquid filtration structure for removing pollutants from fluids. In particular, due to the increase in environmental pollution and population, the lack of drinking water is a pending problem for the whole mankind.
A reverse osmosis membrane, which is a representative conventional separation membrane with high selectivity, provides selectivity to water by allowing only water molecules to pass through a free volume, as a permeation channel, present between polymer chains formed of a polymer constituting an active layer and blocking other molecules or ions. Herein, the free volume as a permeation channel does not have a structure aligned in a direction or a through-type structure, but has a severely tangled or winding structure. Therefore, even a thin active layer has a very complicated and long permeation channel, and, thus, has excellent selectivity but poor permeability.
Meanwhile, a porous separation membrane having a porous structure, such as a nanofilter (NF), and a microfilter (MF) has a through-type porous structure, but it is too large to select water molecules or specific ions. Therefore, the porous separation membrane has excellent permeability but poor selectivity.
Further, a water filtration system in which a recombinant aquaporin is located in a vesicle membrane has poor durability due to instability of a lipid membrane structure.
Accordingly, there has been a demand for the development of a new liquid filtration structure which reduces instability of a lipid membrane structure when using a vesicle filtration system and thus has excellent durability.